Effect of stocking period on pasture species composition, forage production, and animal performance

Authors: Jaramillo, David; FRANCO, ARTHUR - University Of Wisconsin; KOHMANN, MARTA - University Of Wisconsin; RENZ, MARK - University Of Wisconsin

Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2025
Publication Date: 1/31/2025
Citation: Jaramillo, D.M., Franco, A., Kohmann, M., Renz, M. 2025. Effect of stocking period on pasture species composition, forage production, and animal performance. American Forage and Grassland Council Conference Proceedings. January 12-15, 2025.

Interpretive Summary:

Technical Abstract: Increasing the frequency of stocking period has been identified as a management practice for improving productivity and efficiency of resource use in rotationally stocked grazing systems. The potential benefits of frequent rotation include reduction of overgrazed spots, reducing weed competition, improved nutrient redistribution, and improved forage utilization. As pasture productivity, nutritive value, animal performance and ecosystem services can be impacted by the frequency of rotation, this one factor could be resulting in under-production of many of Wisconsin’s 2.7 million acres of pastures. Additionally longer rotation frequencies have been suggested to increase weed establishment and competitiveness in pastures. When weeds are present not only is pasture productivity reduced, but utilization of forages present are reduced and increased injury to livestock can occur. Quantifying differences from an animal and pasture performance perspective will provide key data missing from the literature and allow for evidence-based recommendations to actively change practices of grazing farmers. This study evaluated three stocking periods (1-, 4-, and 8-d; 32-d rest period across treatments) in a randomized complete block design with three replicates in Wisconsin. Pastures were composed of perennial cool-season grasses [mostly orchardgrass (Dactylis glomerata L.) and smooth brome, (Bromus inermis Leyss.)], and legumes (clovers; Trifolium spp.). Weeds present across all pastures were dandelion (Taraxacum officinale Weber ex Wigg.), Canada thistle (Cirsium arvense (L.) Scop.), and yellow foxtail (Setaria pumila (Poir.) Roem. & Schult). Holstein-Angus crossed heifers (~10-12 mo) were used under variable stocking rates, aiming at 1.5 kg DM/kg BW adjusted every 14-d. Herbage mass and nutritive value were assessed every 14-d. In general, treatment had no significant effect on herbage or animal responses. Herbage mass showed a common bi-modal distribution across the growing season, typical of cool-season perennial pastures of the region. Nutritive value was not affected by treatment. The average crude protein and in vitro digestible organic matter concentrations across the season and treatments were 12 and 52%, respectively. Animal average daily gain did not differ across treatments, and was 0.44 kg/head/d, which was below the expected average, likely due to severe drought in 2023. Sum of weed biomass was also similar across treatments (average of 4.63 g DM/m). These results indicate that stocking periods did not affect pasture or animal performance. Further long-term research to assess cumulative treatment effects and animal supplementation would be valuable to inform management practices.